WHOLE CHARACTER
熟shú, shóu
cooked; done (food); ripe; mature; skilled; practiced; familiar; well known
熟 shú is cooked, ripe and well known: 成熟 'mature', 熟练 'skilled', 熟人 'acquaintance'. In casual speech the same meanings sound like shóu — 饭熟了 'the rice is done'.
ZDIC detailed source: 形声,从火,孰( shú)声 — cooking fire under the sound piece 孰, which matches shú exactly.
TOP: THE SOUND PIECE 孰 (SHÚ)
孰shú
who; which (literary)
An archaic graph (shú); when a character keeps it as a piece, the sound role is stated on that character's page.
In 熟: top: the sound piece 孰 (shú) The whole syllable shú matches exactly; the colloquial shóu is the same-meaning spoken variant.
BOTTOM: THE FIRE DOTS
灬huǒ
fire (from 火)
The four-dot bottom fire form; not a standalone page.
In 熟: bottom: the fire dots Shown with its documented or clearly limited role.